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(CNN) — Fort Gordon, a U.S. military base in eastern Georgia, was put on lockdown briefly after someone called 911 — not knowing that an active shooter drill was taking plac there.

The Army installation noted around noon, in a post on its Facebook page, that its gates were being closed “pending an investigation of an alleged incident.”

As it turned out, there was no incident — or, more accurately, not a real one.

A drill was scheduled for, and was underway, Thursday in Fort Gordon’s Darling Hall when “an individual in the building reacted to an event unfolding in the scenario and call(ed) it into 911,” the base explained on Facebook.

“Because Fort Gordon officials were unable to definitely determine whether or not the 911 call was associated with the exercise, Fort Gordon officials took the report as a legitimate threat, canceled the exercise and put the installation on ‪#‎lockdown‬,” the installation noted.

Authorities cleared the building and determined “there was no real-world active shooter,” much less any casualties.

Located in Augusta, Georgia, Fort Gordon is historically and primarily an Army installation — including serving as that branch’s Cyber Center of Excellence and the Signal Regiment.

That said, all four main military services have units at the base. In total, Fort Gordon supports about 13,000 active military personnel, 57,000 of their family living on and outside the base and some 9,000 civilian workers, according to its Facebook page.

It was named for John Brown Gordon, a Confederate lieutenant general — one of the top commanders under Gen. Robert E. Lee. A lawyer, he later became a U.S. senator from and governor for Georgia.

This arrest came after “possible grenades” were found in the man’s vehicle on the grounds, Fort Gordon spokesman Buz Yarnell said then. That man was suspected of stealing military equipment at the base.